Here is what my friend had said about this subject.
MBHD
"Feel free to post the below response.
The SDS EM2 is nearly twenty years old. Yes, twenty years. The poster stated that he knows the owner has had the system for more than fifteen years, so he obviously is aware that the system is at least fifteen years old technology. Electronics change so rapidly that now we consider a piece of hardware a few years old as 'out dated'. How many people are running stand alone EFI systems on their cars which are near twenty years old? I fail to understand why someone would even consider comparing a twenty year old EFI system with anything current. But, for fun, here is some additional information, to help get the facts straight.
Altitude compensation is not needed with a MAP based system. MAF based systems benefit from altitude compensation. If one needs to adjust the tune, while driving, changing altitude or not, then the tune needs to be improved. This holds true for any EFI system.
The SDS primary fuel curve is based on RPM and engine load [manifold vacuum]. The manifold vacuum is not a 'modifier', but an integral part of the fuel curve calculations. Both RPM and engine load are dependant on each other. The modifiers are engine temperature, air temperature, battery voltage, throttle position, tuning knob position (if used) and O2 feedback (if enabled).
A 3-D fuel map was mentioned with other EFI systems. And what is this fuel map based on? RPM and engine load; the same as the SDS. How then can one system be considered 'primitive' while the other system considered not primitive? Both systems use the same parameters to generate the fuel map. A 3-D screen based fuel map is nice if you want to view a graphical representation of your fuel map. This is fine, but does not make you a better tuner, nor does it make you smarter when it comes to understanding what your engine is doing and why it is doing it. It does not help tune your engine. It is just another way to enter parameters to build and develop a correct fuel curve for the engine.
If someone desired to view a 3-D fuel map of the SDS, that would be easily done with any spreadsheet program or graphing software.
Vacuum advance timing, as well as boost retard is available on the twenty year old EM2. Same holds true with RPM based timing. Vacuum advance is programmed in the same way as boost retard.
I do not understand what the poster states when he wrote "the timing is rpm based only for NA applications". He previously stated there was boost retard, but then contradicts himself and states "timing is rpm based only for NA applications". Allow me to hopefully clarify this. You can add timing or remove timing based on RPM. You can add timing or remove timing based on engine load [manifold vacuum]. The two parameters function independently. In this manner, the total timing at any point on the map is the arithmetic sum of both the RPM timing and the load timing; same as any other EFI system. You can have ANY timing you like at any RPM [advance or retard] and you can enter in any timing at any load [vacuum advance, vacuum retard, boost retard or boost advance].
If one needs to verify what I state, they can visit the SDS site and review the EM2 programming instructions. Yes, SDS still has this almost twenty year old information on their site. Take a look
http://www.sdsefi.com/em2def.htm#EM-2D I guess it comes in handy sometimes. lol.
If adjustments of any settings are needed to account for transitions on/off the throttle, then someone needs to work on the tune. This is true for any system.
I respectably disagree with the statement that the owner 'knows the system quite well'. I do not know the owner, nor the application, but based on the below statements, it clearly shows that the owner does not understand the system, regardless of how long the owner has had it installed, which in this case, at least fifteen years.
For example, here is a real world case in point of a properly tuned fuel curve: A friend took a road trip, which included Death Valley California [280 feet below sea level] to Denver, Colorado, [5,280 feet]. The highest elevation was over the Eisenhower Tunnel, which is 11,158 feet. The vehicle is running an SDS EFI system. At no time during the trip was it required to adjust the fuel curve or any other settings. This was over a total of 11,438 foot elevation change. This is an SDS EM4 system, but the programming and features which we are discussing are the same as the EM2.
I understand that, we tend to come to the [incorrect] conclusion that if something we are doing is not working, then it is the fault of the 'product' and not something we are doing. This is especially true when we have lived with the product for enough time that we think we understand it. We continue to do the same things, the same [incorrect] way and therefore, we obtain the same [incorrect] results. We blame this on the product and not on our lack of understanding of the matter at hand.
SDS, Haltec, Holley, Megasquirt, G.M., Electromotive, Edelbrock, F.A.S.T., Nissan, Marelli, Wolf, and others are just some of the EFI systems I have worked with. They are all good and they all do what they need to do, once properly tuned. They all supply the correct amount of fuel and ignition to the engine. No EFI system will work well if not properly set-up or tuned. This is not the fault of the EFI system, but the fault of the installer, owner or tuner.
I hope this does not come across the wrong way, as I am just stating the facts. SDS EFI has been around for longer than most other aftermarket, stand alone EFI systems. For a company to be in business for this many years and still offer the same core product, speaks loudly regarding not only the quality of the product, but its functionality. If the product did not work, as stated by the OP, then it would be impossible for any company survive for over twenty years in a highly competitive arena, such as EFI.
The SDS system is very straight forward in all operational aspects, set-up and tuning wise. If someone is having a difficult time obtaining a proper tune with an SDS system, I wonder what their learning curve will be with a lap-top based system which requires many different variables, tables, pull down menus and check boxes to be properly selected to achieve their goals. This assumes your lap-top communicates with your EFI computer and there is no software, hardware, com port, interface cable, dongle, BIOS, O/S or other issue preventing the EFI computer and the lap-top from establishing communication.
As long as we are having fun here, I will offer [free] tuning assistance to the owner of this vehicle. If he would like a hand in getting his fifteen year project properly tuned, have him PM you his contact information and then forward it to me.
Ray"
